1. Field of the Invention
The present invention relates to an organic-inorganic composite conductive sol comprising colloidal particles of conductive oxide and colloidal particles of conductive polymer, and a process for producing the same. The organic-inorganic composite conductive sol according to the present invention is suitable for use in various fields such as transparent antistatic materials, transparent ultraviolet absorbing materials, transparent heat ray absorbing materials, transparent resistant materials, high refractive index hard coat agents and anti-reflecting agents of resins, plastics, glasses, papers, magnetic tapes, and the like.
2. Description of the Related Art
Antimony oxide-doped tin oxide, tin oxide-doped indium oxide, conductive sinc antimonate, conductive indium antimonate, conductive zinc oxide and the like are known as conductive oxides, and those materials are commercially available in the form of a powder, an aqueous sol or an organic solvent sol.
Japanese Patent Application Laid-open No. Hei 6-219743 (hereinafter simply referred to as "JP-A-") discloses a conductive anhydrous zinc antimonate having ZnO/Sb.sub.2 O.sub.5 molar ratio of 0.8 to 1.2 and a primary particle size of 5 to 500 nm.
JP-A-7-144917 discloses conductive oxide particles comprising indium atom, antimony atom and oxygen atom with the proportion of 1:0.02 to 1.25:1.55 to 4.63 in the molar ratio of In:Sb:O, and having a primary particle size of 5 to 500 nm. It also discloses conductive oxide particles having a crystal structure of indium antimonate, comprising indium atom, antimony atom and oxygen atom with the proportion of 1: 0.83 to 1.25:3.58 to 4.63 in the molar ratio of In:Sb:O, and having a primary particle size of 5 to 500 nm.
Polyaniline, polyaniline derivatives, polythiophene, polythiophene derivatives, polypyrrole, polyacetylene, polyparaphenylene, polyphenylene vinylene and the like are known as a conductive polymer.
JP-A-6-287454 discloses a water-soluble conductive material containing a polymer such as polyaniline, polythiophene, polypyrrole, or poly(paraphenylene sulfide).
JP-A-5-170904 discloses a polyaniline derivative which is soluble in an organic solvent and shows high electric conductivity by doping.
JP-A-171010 discloses a conductive polymeric compound solution containing polyaniline or its derivative in a concentration of 0.5% by weight or more, or a conductive polymeric compound of polythiophene substituted by alkyl groups having 4 or more carbon number, and a diamine compound in an amount of 2 mol % or more to monomers constituting this conductive polymeric compound.
JP-A-6-76652 discloses a process which comprises contacting a solution obtained by dissolving monomer of pyrrole type, furan type, thiophene type, aniline type, benzidine type or the like in a solvent with a polymeric molded article by impregnating in the solution, and contacting with an oxidizing agent, thereby rendering the surface of the polymeric molded article conductive.
JP-A-1-313521, 7-90060 and 9-12968 disclose polythiophehe and polythiophene derivative, and a transparent antistatic coating agent comprising those composition.
Conductive oxide and conductive polymer can be used to an antistatic treatment of plastic molded articles, films and the like by mixing the same with an appropriate organic binder. In particular, a sol of conductive oxide fine particles having high transparency can be used as a transparent antistatic paint, utilizing the characteristics of the fine particles. The conductive oxide is electron-conductive. Therefore, if It is used as, for example, a transparent antistatic paint, conductivity of a coating layer is stable, and it also has an effect as an inorganic filler, so that a coating layer having high hardness can be obtained In a method using only the conductive oxide, if the amount of the conductive oxide blended to a binder increases, good conductivity can be obtained, and no problem arises on coloration of a coating layer. However, use of only the conductive oxide has the problems that transparency or flexibility of the coating layer decreases, and if the amount blended therein is decreased, it is difficult to develop conductivity. Further, if a process of, for example, drawing a coating layer and a substrate is conducted after the formation of the coating layer, distance between mutual conductive oxide particles becomes large, so that the problem arises such that the conductivity lowers.
On the other hand, the conductive polymer has a relatively good film-formability by itself, and therefore can be used alone depending on the use. However, since the conductive polymer is in the form of a colloidal solution, coating layer strength is weak, and in order to put it into practical use, it is necessary for use to mix the same with an organic binder, similar to the conductive oxide. If the blending amount of the conductive polymer to the organic binder is large, it shows a good conductivity, but where used as, for example, a transparent antistatic paint, there are disadvantages that the coloration of a coating layer increases, thereby decreasing transparency, and it is difficult to develop a coating layer hardness although flexibility of a film is excellent. Further, since the conductive polymer colloid consists of very fine particles, there are disadvantages that compatibility with a binder is poor and viscosity increases. Furthermore, if the amount of the conductive polymer blended is small, it is difficult to develop conductivity. It is also difficult for the conductive film using the conductive polymer to increase the thickness of the film from the view point of coloration and costs, so that it is difficult to obtain stability in conductivity of a film
Where the conductive oxide colloid or conductive polymer colloid is used as an antistatic use, for example, where it is used as a transparent antistatic paint or where the sole use of the conductive oxide colloid or conductive polymer colloid does not exhibit a sufficient performance, for example where the blending amount is small or a coating layer is post-processed, defects of both the conductive oxide colloid and the conductive polymer colloid cannot be supplemented by merely mixing and using together the conductive oxide sol and the conductive polymer solution. In general, even if the conductive oxide sol and the conductive polymer are merely mixed, agglomeration and gelation occur, and such a product cannot be put into practical use.